Certain naturally occurring materials such as oil shale, tar sands, and diactomaceous earth contain a hydrocarbonaceous component which upon heating releases volatile hydrocarbon vapors. Various methods for retorting these materials to produce the pyrolysis vapor have been described. See for example U.S. Pat. Nos. 4,199,432; 4,312,740; 3,008,894; and 3,703,442. In many of these process schemes an inert gas, i.e., a non-oxidizing gas, is used in the retort or in some other step of the process. Superheated steam is often a preferred gas for this purpose.
The use of superheated steam in a retorting process presents several problems which must be overcome if it is to be used in a commercial synthetic petroleum process. In areas where the raw materials are normally found, water for producing the steam is usually not readily available due to the arid climate. This makes recycling of the process steam condensate essential. However, contamination of the steam condensate and process water with salts as a result of the process usually requires expensive cleanup steps before the combined water can be recycled. Otherwise, the accumulation of salts in the pipes and steamtubes will result in equipment failures.
The present process involves a means for preparing superheated steam from recycled steam condensate and process water of variable quality while avoiding equipment fouling.